For patients with aching muscles and sore joints, the application of heat can decrease the viscosity of fluids, loosen stiff muscles, improve blood flow to the affected area, facilitating tissue repair, and creating a feeling of relaxation. For some acute injuries, the application of cold can numb pain, constrict blood vessels and mitigate the inflammatory response. The application of heat to the skin as a means to penetrate deeper into tissues has historically been used for pain relief of muscles and joints, as well as for the treatment of certain inflammatory conditions. The application of cold materials to the skin has also been used for similar treatments, especially for treating inflammatory responses such as joint inflammation.
Traditional heating devices have, in some instances, generated heat using chemical formulations, such as iron powder formulations, that oxidize when exposed to air. Commercially available thermal chemical formulation products are mainly categorized with disposable heat patches, which are available as loosely formed fabric thermally active components filled with the exothermic composition. An alternate means of providing heat is by way of electrical heating elements that are attached to a power source. Since the desired time of use is often longer than 4 hours, in the case of an electrical source, the power source typically used in these types of devices is either an electrical wall outlet or a battery.
Other chemical heating devices include those products that incorporate heating portions into fabrics that can conform or are shaped to fit various parts of the body, such as the knee or the back as shown in U.S. Pat. No. 6,074,413. In these cases, typically the entire product, including the garment and the heat providing exothermic formulation materials, are disposable because they are incorporated into a unitary product. The chemical heating portion is not removable from such a unitary product, and therefore, the entire device is designed to be disposed following use. Each use can typically last for 6 to 12 hours, and a user can use 2-3 of these products over a 24-hour period. These types of products have the disadvantage of having loose powder formulations that do not always adequately conform to parts of the skin and do not conduct heat thoroughly to the skin since a woven or non-woven fabric surface is in contact with the skin.
Other types of devices, such as those shown in U.S. Pat. No. 5,484,366, exemplify elements that are not disposable, such as using a back belt with gel insert containers. In such a device the gel-inserts must be manually re-heated or cooled, taking more active participation by the user in order to be reusable. Similarly, the device shown in U.S. Pat. No. 6,416,534 uses a back belt with a flexible fabric, and a gel insert that is reheated using electrical heat. This type of device also involves active participation on the part of the user and a potential lag time in order to heat the gel-insert. U.S. Pat. No. 6,074,413 is directed to a disposable thermal back wrap having one or more thermal inserts comprising a plurality of heat cells, wherein heat is applied to specific areas of the user's back, for pain relief. U.S. Pat. No. 5,605,144 is directed to a heating garment with pouch for accommodating inserted chemical heating inserts that are air activated.
U.S. Pat. No. 5,484,366 is directed to an aerobic/cross training exercise belt. The belt comprises a straight piece of material having a fastener on each end whereby the ends can be fastened together to form a closed belt. A back lumbar support is connected to the rear body of the belt. The back lumbar support has at least one pocket to mount chemical gel-inserts whereby the user would have a thermal application to the lumbar area while wear wearing the belt. The gel inserts can be heated or cooled to the desired temperature. U.S. Pat. No. 6,623,419 is directed to a therapeutic back belt and related method of manufacture. The belt includes magnets that are secured to the belt and thermally active gel material. U.S. Pat. No. 5,179,942 is directed to a lumbar support therapeutic heat/cooling/air belt. The support has one pocket in the lower back section that is capable of receiving a insert to create a thermal change or provide air for support purposes.
Additional devices have also been disclosed, as shown in U.S. Pat. No. 7,147,610, that incorporate massaging elements with the heating elements so that they are conveniently available in a single device. Such a device involves excess bulk, is non-discreet and requires the use of external power sources (i.e. a junction box) since the heating and massaging element require the use of electrical power. In addition, although the parts are reusable, electrical elements tend to be non-washable. Published U.S. Patent Application 2004/0082886 is directed to a therapeutic device for relieving pain and stress in the hands and feet. The portable device provides heat and vibratory therapies for the hand or foot.
U.S. Pat. No. 5,925,072 is directed to a disposable elastic thermal insert wherein iron powder based exothermic compositions are segmented into individual portions and integrated into a back belt. In this composition, the thermal conductivity is not optimized since the composition is separated from the skin by a fabric barrier. U.S. Pat. No. 5,918,590 is directed to a specific heat cell unit comprising an iron powder based exothermic composition, wherein a specific exothermic formulation and pocket fill volume are defined.
U.S. Pat. No. 6,146,342 is directed to massage pad having a plurality of randomly actuated pressure inducing elements. The apparatus massages the body by subjecting the body to impacts from reciprocating plungers. The plungers are secured in a flat array within a flexible pad. Each plunger has an associated solenoid device that alternately causes the plunger to project from the pad and to retract within the pad. An electrical circuit includes a power cord and plug assembly, manual controls disposed serially on the cord and plug assembly, and a controller generating operating signals randomly to the solenoids. A heating element is optionally included in the flexible pad, with a suitable controller provided among the controls.
Still other types of devices, as shown in U.S. Pat. No. 7,077,858, include those that use flexible heat exchangers to distribute cooling and heating agents to the skin utilizing electrical heat. U.S. Pat. No. 6,409,748 is directed to a heating pad with removable gel insert that provides rapid initial warming. U.S. Pat. No. 4,846,176 is directed to a thermal bandage having a conformable region that can be placed against the skin to uniformly heat or cool the contacted skin area.